Enantioselective Alkylation of Aldehydes Using Functionalized Alkylboron Reagents Catalyzed by a Chiral Titanium Complex

A practical method is developed for the synthesis of enantioenriched functionalized secondary alcohols through catalytic enantioselective alkylation of aldehydes. Functionalized alkylboron reagents, [FG–(CH2) n ]3B (FG = Br, TIPSO, PhtN, CO2 i Pr, and CN) prepared from terminal olefin precursors by hydroboration, undergo enantioselective addition to aldehydes in the presence of a catalytic amount (5 mol %) of 3-(3,5-diphenylphenyl)-H8-BINOL and excess titanium tetraisopropoxide to afford the corresponding functionalized alcohols in high enantioselectivities up to 99% ee.